Exam 13: Extensions of and Deviations From Mendelian Genetic Principles

In the human ABO blood system,the allele i is dominant to I^A and I^B.

Comb shape in chickens is controlled by

Solid black,black with tan belly,and agouti coat color in mice are all caused by alleles of the agouti gene.All three colors can be true-breeding.When using mice from true-breeding strains: (1)Black × Agouti F₁s are all agouti,(2)Black × Black with Tan belly F₁s are all black and tan,and (3)Black with Tan belly × Agouti F₁s are all agouti.If you were to cross the F₁s from (1)with the F₁s from (2),what proportion of the resulting offspring would you expect to be black with a tan belly?

Mutants that make up a complementation group complement each other.

In chickens,there is a mutant gene called "frizzle" that results in weak,stringy,and easily broken feathers.When a frightfully frizzled fowl is bred to a normal chicken,the offspring are all mildly frizzled.If one breeds two mildly frizzled chickens to each other,the offspring have the phenotypic ratio of 1 normal: 2 mildly frizzled: 1 frightfully frizzled.What is the mode of inheritance of "frizzle"?

Individuals with neurofibromatosis may have a range of phenotypes,from pigment spots on the skin to tumorlike growths.This is an example of

Two true-breeding mutant strains of Drosophila have black body color instead of the wild-type gray yellow.When the two strains are crossed,all the F₁ flies have wild-type body color.How can these data be interpreted?

Why is it that human males and females who are both heterozygous for the pattern-baldness gene have different phenotypes (males are bald,females are not bald)?

Dextral (D) and sinistral (d) shell coiling in the water snail Limnaea peregra is genetically determined. From a population of mixed sinistral and dextral snails, a sinistral female and a dextral male are chosen. All the offspring are dextral. When the female offspring are mated, 50% produce only sinistral snails and the other 50% produce only dextral snails. -This form of inheritance is called

The 9:6:1 F₂ ratio found in fruit shape in summer squash is a deviation from an expected Mendelian ratio.What does this represent?

Feather color in chickens is the result of an incompletely dominant gene. The gene responsible for black feathers (B) when homozygous results in a muted color called "Andalusian blue" if combined with an allele for white feathers (b). When the white allele occurs in homozygous conditions, a white phenotype results. A gene affecting comb shape (R), which results in a comb called a "rose" comb, is completely dominant over (r), which in homozygous conditions results in a comb called "single." A mating between a black single rooster and white rose hen results in a number of chicks, all of which have identical phenotypes. -What is the phenotype and genotype of the chicks?

In the multiple allelic system for eye color in Drosophila,the phenotypic expression of the alleles depends on

Which of the following will result in modifications to the expected Mendelian ratios?

For a gene with complete dominance,the recessive allele has no effect on the phenotype of a heterozygote.

Familial hypercholesterolemia is a genetic disease that affects approximately one in 500 people worldwide.There is more than one genetic cause of the disease.Class I is often described as an autosomal dominant disease.Affected individuals have cholesterol levels >250 as children and often >300 as adults.However,homozygotes have cholesterol levels of >600 as children and can die of heart attacks in their 20s.These individuals entirely lack a functional LDL receptor.Which of the following would be the best description of the inheritance of this form of hypercholesterolemia?

What is the number of possible genotypes in a multiple allele series with 6 alleles? How many of these are homozygous and how many are heterozygous?

Recessive lethals are often mutations in essential genes.

Feather color in chickens is the result of an incompletely dominant gene. The gene responsible for black feathers (B) when homozygous results in a muted color called "Andalusian blue" if combined with an allele for white feathers (b). When the white allele occurs in homozygous conditions, a white phenotype results. A gene affecting comb shape (R), which results in a comb called a "rose" comb, is completely dominant over (r), which in homozygous conditions results in a comb called "single." A mating between a black single rooster and white rose hen results in a number of chicks, all of which have identical phenotypes. -Use a Punnett square to demonstrate a cross between two of the F₁ offspring.What are the phenotypes and ratios that occur?